1. Field of the Invention
The present invention relates to a liquid cooling jacket attached to a heating element in a liquid cooling system used for cooling an electronic device.
2. Description of the Related Art
Conventionally, a liquid cooling jacket used for cooling an electronic device must efficiently transmit heat from a heating element to coolant.
For this reason, as an example, a conventional liquid cooling jacket has therein a meandering passage, as illustrated in FIG. 18. In this example, the passage 1302 within the jacket 1301 meanders so that the flow 1303 of coolant is in contact with the jacket 1301 as long as possible. This is a method in which the contact area between the coolant and the inner surface of the jacket wall is increased by increasing the length of the passage within the jacket 1301 as much as possible to efficiently transmit heat from a heating element to the coolant.
In another example, as illustrated in FIG. 19, the flow 1401 of coolant is divided into a plurality of streams 1403a to 1403f. This is a method in which provision of a plurality of passage paths decreases the passage resistance and increases the contact area between the coolant and radiating fins 1402 to efficiently transmit heat (for example, see JP-A-2000-340727).
In addition, because convenience of piping is superior if the inlet and outlet of coolant are in a row, a conventional liquid cooling jacket has the inlet and outlet of coolant arranged in a row. As illustrated in FIG. 20, this is a method in which a partition 1502 is provided at the center of the arrangement of radiating fins 1501 to turn back the flow 1401 of coolant and thereby the inlet and outlet are arranged in a row (for example, see JP-A-2002-170915).
However, the meandering passage as illustrated in FIG. 18 has a problem that the passage resistance increases as the length of the passage increases, and thus the pressure loss increases.
The passage in which the flow of coolant is divided into a plurality of steams, as illustrated in FIG. 19, has a problem that it is difficult to make the coolant flow evenly among the radiating fins. More specifically, because any liquid flow has straight motility, there is a problem that the coolant is hard to flow to the radiating fin near the inlet. Thus, as illustrated in FIG. 19, unevenness occurs in the flow rates of the streams 1403a to 1403f. As a result, the heat transfer coefficient decreases so that heat from the heating element cannot be efficiently transmitted to the coolant.
The structure as illustrated in FIG. 20 also has a problem that unevenness occurs in the liquid streams 1503a to 1503c between the radiating fins. More specifically, the flow rate of the stream 1503b near the inlet or outlet is the highest and the other flow rates of the streams 1503a and 1503c are lower. As a result, the heat transfer coefficient decreases so that heat from the heating element cannot be efficiently transmitted to the coolant.
In addition, any prior art as described above has a problem that improvement of coefficient of thermal conductivity is difficult even if the jacket size is increased in order to ensure more contact area, because the distance from the centered heating element increases. More specifically, conventionally, as illustrated in FIG. 21, a base 301 horizontally spreads heat to transmit the heat to each radiating fin 302. However, the base thickness t1 has a limit by the influence of weight and height. Actually, the thickness is about 7 mm at the maximum. Therefore, the spread 303 of heat is limited to the periphery of the heating element 103 and heat cannot be transmitted to the end radiating fins 302a. That is, as the jacket size increases, the cooling effect of the end radiating fins decreases.